Backflow Prevention

What is Backflow?

Backflow refers to the reverse flow of non-potable water, or other substances, through a cross-connection and into the piping of a public water system or customer’s potable water system. Two types of backflows are backpressure backflow and back-siphonage. 

What is a Backflow Prevention Device?

A backflow prevention assembly is a means or mechanism to prevent backflow.  The basic means for preventing backflow is an air gap, which either eliminates a cross-connection or provides a barrier from backflow.  The basic mechanism for preventing backflow is a mechanical backflow preventer, which provides a physical barrier to backflow.  The principal types of backflow preventers are the reduced-pressure principal assembly, the pressure vacuum breaker assembly and the double check valve assembly.

What is Backpressure Backflow?

Backpressure backflow occurs when the downstream side of the piping system is greater than the supply pressure in a public system or customer’s potable water system.  Backpressure can result from an increase in downstream pressure, a reduction in the potable water supply pressure or a combination of both.  Pumps can create increases in downstream pressure; temperature increases in boilers, etc.  Reductions in potable water supply pressure occur whenever the amount of after being used exceeds the amount of water being supplied, such as during waterline flushing, firefighting or breaks in the water mains.

What is a Cross-connection?

A cross-connection is any temporary or permanent connection between a public water system or the customer’s potable water system and any source or system containing non-potable water or other substances.

Common Cross-Connections:

Private Wells – where the private well connection is connected to a service line receiving water from a public water supply.  The untreated water could be pumped into the potable water supply which serves the home and the public water system.

Lawn sprinkler systems – where the stagnant/contaminated water from the sprinkler system could be drawn into the drinkable water supply for your home.

What can I do to help prevent a Cross-connection?

Without the proper protection something as simple as a garden hose has the potential to contaminate or pollute the drinking water lines in your house. In fact over half of the country’s cross-connection incidents involve unprotected garden hoses. There are very simple steps that you as a drinking water user can take to prevent such hazards, they are:

• NEVER submerge a hose in soapy water buckets, pet watering containers, pool, tubs, sinks, drains or chemicals.
• NEVER attach a hose to a garden sprayer without the proper backflow preventer.
• Buy and install a hose bibb vacuum breaker in any threaded water fixture. The installation can be as easy as attaching a garden hose to a spigot. This inexpensive device is available at most hardware stores and home-improvement centers.
• Identify and be aware of potential cross-connections to your waterline.
• Buy appliances and equipment with a backflow preventer.
• Buy and install backflow prevention devices or assemblies for all high and moderate hazard connections.

Why do cities need a Cross-Connection and backflow testing program?

These programs safeguard the public drinking water and protect the health of its residents.  They do this by helping to ensure that any contaminants that could backflow into the public water supply system are isolated within the internal distribution system.  

Backflow Assembly Testers for Smithfield City

Links

Backflow Prevention YouTube Video

Backsiphonage YouTube Video

Smithfield City Cross Connection Municipal Code

General Responsibilities of Public Water Systems Document

50 Cross-Connection Questions, Answers & Illustrations